78 Intelligence and Miscellaneous Articles. 



size of the nuggets sometimes found in the gravels, compared with 

 that of the nuggets met with in the gold-bearing quartz-veins 

 (usually from about l^dvvt. to |^oz., though occasionally as much as 

 1 2 ozs. or even 13 lbs.), the upper portions of the veins, now ground 

 down into gravel, were probably richer in gold (as formerly sug- 

 gested) than the lower parts, now remaining. As far as actual 

 mining experience shows, some of the " quartz- reefs" in Victoria 

 prove as rich in gold at a depth of 200, 230, and 400 feet as at the 

 surface ; the yield, however, fluctuates at any depth yet reached. 

 According to the author's latest observations, the gold-drifts, and 

 their accompanying basaltic lavas, are of Pliocene and Post-pliocene 

 age. Miocene beds occur at Corio Bay, Cape Otway coast, Murray 

 basin, and Brighton; and Eocene beds on the east shore of Port 

 Phillip, Muddy Creek, and Hamilton. Two silicified fossils (Echi- 

 noderra and Coral), thought by Prof. M'Coy to be of Cretaceous 

 origin, have been found in the gravel near Melbourne. 



This letter also contains some remarks on the probability of some 

 of the coal of Eastern Victoria being of " Carboniferous" age, — on 

 the occurrence of Silurian fossils in the rocks of all the gold-districts, 

 — on the newly- discovered bone- cave at Gisborne, about twenty-five 

 miles north of Melbourne, — and on the progress of the Geological 

 Survey of the Colony. 



XIV. Intelligence and Miscellaneous Articles. 



ON THERMOGRAPHY, OR THE ACTION OF HEAT CONSIDERED AS A 

 MEANS OF PRODUCING IMAGES ON SENSITIVE PAPER. BY 

 M. NIEPCE DE SAINT-VICTOR. 



THE experiments I am about to describe are an extension of 

 those of Messrs. Moser, Knorr, and Draper. I believe I have 

 succeeded in adding to the facts already established a considerable 

 number of new and interesting observations, of a kind calculated to 

 throw some light on this class of phsenomena. 



If, upon a metallic plate, heated by contact with boiling water, 

 you place an engraving, or page of writing printed in unctuous 

 ink, and lay upon that a sheet of paper rendered sensitive, first with 

 nitrate of silver, and then with chloride of gold, you will obtain 

 a violet-blue image of the dark parts of the engraving or letters. 

 If, however, the paper be prepared with nitrate of silver only, the 

 lights of the engraving are reproduced of a dark (bistre) colour. 



With paper prepared with the salts both of gold and silver, large 

 printed letters will produce an image even at a distance of several 

 millimetres ; but if a continuous, though thin, plate of mica, or 

 metal, or even a sheet of vegetable paper be interposed, no image 

 will be produced. 



Drawings in aqueous ink, in black-lead, or in charcoal, produce no 

 image when on ordinary paper ; but they do when on vegetable paper. 



Plates and flat surfaces of varnished porcelain, with black letters 

 or coloured drawings, which have been subjected to the action 

 of fire, but have not been enamelled, have afforded me impressions ; 

 but letters or drawings on enamelled porcelain produce no image. 



